Drcoffee

The 1/2" hose on the front valve cover ( bank 2 ) is a fresh air source for the pcv. Air flows from the air cleaner into the valve cover, not the reverse. If you have oily vapors flowing into the intake from there, you have problems. Most likely piston ring blowby which pressurizes the crankcase. More pressure than the pcv can handle. This results in your plastic intake tube coated in oil and the throttle plate black with carbon. Pull yours off and check inside the tube where that port is located. If you see oil, you have blowby.

The pcv valve serves two purposes. One is to meter the air flow out of the valve cover. Second is to prevent a backfire from entering the valve cover. It immediately closes the valve under pressure. Try blowing into the pcv on the hose side. It locks down. Thats why the front hose should never see vapors going into the intake. There is no valve there.

To take it further, if you pull vacuum on both valve covers, you create a vacuum without relief and that can suck your gaskets out of place. Pan gaskets, main seals, cam seals. You want vacuum but not absolute vacuum in crankcase.

Drcoffee

While searching youtube for pcv vids I came across one that talked about new systems that do not have a pcv valve but a fixed orifice port. If you look at the size of the hole it confirms to me that the pcv port can be restricted without harm to the engine. I'm leaning towards the idea that the intake puts too much vacuum on the pcv valve and is sucking oil out because of it. I may step the restriction down another size if I dont see a benefit at 1/4".

salimshah

Going along with your chain of thought .. smaller dia will reduce flow, but re-consider how the oil is jumping the the air gap. If there is no air gap (oil level has risen up) then for sure it will be sucked up. If there is an air gap then only vapors get sucked in (normal operation).

Salim

Drcoffee

I agree with you. What causes the oil level to rise is the vacuum created in the valve cover. If you can reduce the volume of vacuum in the valve cover, you are lessening the air flow up from the crankcase, allowing better drainage of oil down from the head. and reducing the pull of oil up under the baffle in the valve cover increasing the air gap you speak of.

fastnoypi

I will have to disagree on some points. Anytime the throttle body is in an open position, airflow is creating a vacuum effect on the front valve cover. Everyone has a certain amount of blowby. There is no way a backfire can enter the valve cover in the way this Toyota v6 pcv is setup. The pcv is setup in such a way that it is just a breather for the air/oil separator function of the rear valve cover. The intake and exhaust valves are on the bottom part of the head where any combustion or detonation can take place.

Drcoffee

Fast,
I just want to make sure we are talking about the same thing. A backfire is when the combustion in one of the cylinders occurs while the intake valve is open. The fireball then travels up into the intake plenum and will enter the pcv hose from the plenum. If that's how you see it, then okay.

Drcoffee

If you cant tell, I love problem solving. I wish I had noticed this before installing the valve cover but has it occured to anyone to move the PCV valve to top of the vent chamber? The aluminum is thick enough to drill and tap the cover just to the right of the pcv valve in the taller chamber. Then cap off the original opening.
In this way, the pcv valve isnt sucking the liquid oil off the inner surface of the baffle.

fastnoypi

That's the way i understand a backfire aka "pre-det"...your statement regarding "backfire from entering the valve cover" I have issues with because no ignition happens inside the valve cover. Backfire would traverse on the intake channels of the head, not the valve area.


As far as tapping the top of the vent cover, i had thought about it but due to downtime and urgency that the RX needed to be on the road, i had no time to attempt. The tapered thread PCV's use, i also dont have a BSPT tap. Its not a standard NPT thread. IMO, raising it higher is still a temporary solution for earlier v1 and v2 valve covers. Spacing the PCV up higher will buy time for the oil to drain down from the baffles. The drainage has be be addressed. The holes are simply too small on the baffle covers with less than 1 mm between the stamped plate. The drain holes easily get clogged with cold air whipped oil when trip durations are very short. Of course that is still theory, feel free to relocate the PCV and report real world results!

Another poster either on CL or Toyota Nation, gave me another idea that i would consider attempting if i really had the time. He drilled out the rivets holding the stamped plate against the valve cover for deep internal cleaning. Knowing where the tiny baffle drains are and relation to the cams, i would look for a place to drill larger relief drains for the baffles.

Drcoffee

It looks like I wont have enough tme to drive it to determine if the oil loss is pcv related just by oil volume. So I decided to use a makeshift oil catch can out of an air compressor fliter from the hardware store. The valve at the bottom was filled with RTV to seal the opening. Once I get a chance to drive it on the highway, we will find out if its still drinking oil or if there is any oil loss, it is probably piston ring related. I fixed the gasket leaks already.

the filter is zip tied to the cross brace.
Newly installed


After 30 miles with 15 miles under 60mph and 15 miles between 70-80 mph. The big test will be a four hour drive on the highway tomorrow.


Personally, I believe the vacuum is too strong. I will pick up a 1/8" restriction tomorrow if the oil collection is too much.

Drcoffee

I found something interesting over ob bobstheoilguy site regarding excessive oil consuption in their 5.3L engines. A TSB which directs the dealer to switch from a pcv valve to a fixed orifice tube type.

Higher Than Expected Engine Oil Consumption (Replace PCV Valve) #01-06-01-029
Higher than Expected Engine Oil Consumption (Replace PCV Valve)
1999-2002 Chevrolet and GMC C/K Models

2002 Cadillac Escalade

with 5.3L or 6.0L Engine (VINs T, N, U - RPOs LM7, LQ9, LQ4)

Condition
Some customers may comment on higher than expected engine oil consumption. They may further comment on consumption in the range of 2,000 miles (3,200 km) or less per quart (0.946 liter) of oil under normal driving conditions.

Cause
The condition may be due to the PCV Valve flow rate under certain engine operating conditions.

Correction
Verify that the oil consumption is not the result of an oil leak or other engine concern.
Dealer should perform an oil consumption test. The vehicle should have accumulated over 4,000 miles (6,450 km) before establishing the oil consumption rate. Reference Service Bulletin #01-06-01-011, Information on Engine Oil Consumption Guideline, for details.
Remove the PCV Valve and inspect the hose going to the intake manifold for signs of excessive oil being present.
If excessive oil is present in the PCV hose, replace the PCV Valve Type 948C (2) with a new-style fixed orifice PCV Valve Type CV2001-C (1). See Fig. 1 - PCV Valve Identification.
FIGURE Figure 1 -- PCV Valve Identification(c)

salimshah

DrCoffee:

Have you stitched to the newer version of valve cover?
How much oil have you picked up in your catch-can ... I think the collection bottle is 1/20 of a qt.

Salim

Drcoffee

Just drove 110 hwy miles (2 hrs). This is what i collected and yes, I switched to the Gen2 valve cover from a 2004 RX300.

Much more oil than I would like to see in such a short distance. I will reduce the restriction to 1/8" and retest

I will say though, that small amount of oil in added to 6 gallons of gasoline during combustion is no real concern to me. But the accumulated oil loss is bothersome.

fastnoypi

Did you do any prep work on the gen2 valve cover (solvents, air pressure,etc.. to determine any existing internal baffle sludge) prior to installation?

Drcoffee

Yes. It was solvent washed before I got it and I flushed it with brake cleaner until it was clear and blew it out with compressed air and it flowed great.

edit: finished 220 mile round trip on the highway running at 75 mph using the 1/4" restrictor in the hose.

this is far too much oil being burnt. There was some good news tho. Based on the fuel gauge, it looks like my gas mileage has improved from 19.5 to 23 mpg since making the change in the PCV and adding the oil catch can. The next step is to re-test with the 1/8" restrictor. if I still get oil in tHe catch can but less than before, I would be satisfied that there is still sufficient vacuum to maintain pcv function. At that point I would gut the pcv valve and re-test again running only 1/8" restrictor.



This vacuum splice is cut so that one end is 1/8" and the other is 1/4" in diameter. $3 at autozone

Drcoffee

Fast and Salim,

you may be on to something. While I have the oil catch can connected, I decided to buy some plumbing to raise the the PCV valve outside of the valve cover. There is limited space directly above the pcv. I used a 90* 3/8" brass male/female, then a short male/male and a female/female. The pcv threads in nicely. The difference between NPT and BSPT is the angle of the threads. NPT is 60* and BSPT is 55*, NPT is 18TPI and BSPT is 19TPI.
The elbow turned in 1.5 turns. I didn't want to risk cracking the valve cover so I used oil and gas teflon tape with about 4 wraps to seal any gaps in the threads and to prevent dissimilar metals reacting. I'm not sure if aluminum and brass react but this should help. So the brass pipe and pcv point towards the passenger front tire, upwards at a 30* angle from horizontal. The plan is to limit the vacuum of the pcv orifice on the baffle inside the valve cover and allow any oil that migrates up into the brass pipe a chance to drain back to the valve cover. I still have the 1/4" restrictor in the line.

If this prevent oil loss I will search out BSPT fittings to replace the NPT and make it permanent. If it fails, then I will move back to a 1/8" restrictor in the hose and gut the valve.

Edit: this test failed. After running the engine briefly in the garage, I could see the oil flowing into the catch can. I then added the 1/8" restrictor in the line and the oil continued to flow into the catch can. I will have to remove the brass piping and restore the pcv into the valve cover.

The oil is not flowing like a river, but you can see the atomized oil condensing in the can. Filling it a rate greater than before.

follow up:
I removed the brass components and restored the pcv valve to the valve cover and left the 1/8" restrictor in the line. When I restarted the engine there was no sign of oil in the catch can. Very strange indeed. So I disconnected the hose just after the restrictor and there was a noticable amount of vacuum even with the restriction. I will run it this way for a few days and see if any oil is caught in the can. And keep an eye on the fresh air port on the left valve cover to make sure there isnt an increase in oil going that way as a result of blowby.

This may appear to be an exercise in futility but it answers questions other have proposed but havent acted on. And its fun.